Auxiliary vertical magnet outside a nested unbalanced magnetron

Abstract

An unbalanced magnetron rotatable about the back of a sputtering target and including a nested magnetron part having an outer magnetic pole of a first magnetic polarity surrounding an inner magnetic pole of an opposed second magnetic polarity and an auxiliary magnet increasing the unbalance and adjusting the uniformity of sputtering. In a first embodiment, the auxiliary magnet is vertically magnetized and placed on an opposite side of the rotation axis from the major portion of the nested magnetron part. This embodiment most strongly affects the vertical magnetic field distribution near the wafer and can produce a more uniform magnetic field at the wafer. In a second embodiment, the auxiliary magnet is horizontally magnetized and placed between the inner pole and the portion of the outer pole near the target periphery. This embodiment most strongly affects the sputtering erosion pattern near the target periphery. The two embodiments can be combined.

What is claimed is:  
     
       1. A sputtering magnetron, comprising: 
       a nested unbalanced magnetron positionable at a back of a sputtering target, rotatable about a center axis of said target, and comprising an outer magnetic pole of a first magnetic polarity parallel to said center axis and surrounding an inner magnetic pole of an opposite second magnetic polarity, a total magnetic flux of said outer magnetic pole being at least 150% of a total magnetic flux of said inner magnetic pole; and  
       an auxiliary permanent magnet magnetized along said center axis with said first magnetic polarity, positioned on an opposite side of said center axis from said inner magnetic pole, and rotatable with said nested unbalanced magnetron.  
     
     
       2. The magnetron of  claim 1 , further comprising a second auxiliary magnet magnetized perpendicular to said center axis and positioned between said inner magnetic pole and said outer magnetic pole on a side of said inner magnetic pole opposite said center axis. 
     
     
       3. A sputtering magnetron, comprising: 
       a nested unbalanced magnetron positionable at a back of a sputtering target, rotatable about a center axis of said target, and comprising an outer magnetic pole of a first magnetic polarity along said center axis and surrounding an inner magnetic pole of an opposite, second polarity, a total magnetic flux of said outer magnetic pole being at least 150% of a total magnetic flux of said inner magnetic pole; and  
       an auxiliary permanent magnet magnetized along said center axis, rotatable with said nested unbalanced magnetron, and positioned on a side of said center axis opposite said inner magnetic pole, and positioned outside of said outer magnetic pole.  
     
     
       4. The magnetron of  claim 3 , wherein said auxiliary magnet is of said first magnetic polarity. 
     
     
       5. A sputtering magnetron, comprising: 
       a nested unbalanced magnetron positionable at a back of a sputtering target, rotatable about a center axis of said target, and comprising an outer magnetic pole including  
       a plurality of first magnets of a first magnetic polarity along said center axis, and  
       a pole face band magnetically coupling said first magnets and surrounding an inner magnetic pole of an opposite magnetic polarity,  
       wherein a total magnetic flux of said outer magnetic pole is at least 150% of a total magnetic flux of said inner magnetic pole; and  
       an auxiliary permanent magnet magnetized along said center axis, rotatable with said nested unbalanced magnetron, and positioned outside of said pole face band and on an opposite side of said center axis from said inner magnetic pole.  
     
     
       6. The magnetron of  claim 5 , wherein said auxiliary magnet is of said first magnetic polarity. 
     
     
       7. A magnetron configured for use in a plasma sputtering reactor having a target and a pedestal for supporting a substrate, comprising: 
       a nested unbalanced magnetron positionable at a back of said target and rotatable about a center axis of said target and comprising an inner magnetic pole of a first magnetic polarity producing a first total magnetic flux and an outer pole of an opposed second magnetic polarity surrounding said inner magnetic pole and producing a second total magnetic flux; and  
       an auxiliary permanent magnet magnetized parallel to said center axis and rotatable with said nested unbalanced magnetron and positioned outside of said outer magnetic pole and on an opposite side of said center axis from said inner magnetic pole.  
     
     
       8. The magnetron of  claim 7 , wherein a value of a maximum vertical magnetic field produced by said nested unbalanced magnetron at a surface of said pedestal is within a factor of two of a value of a maximum vertical magnetic field produced by said auxiliary magnet at said surface of said pedestal. 
     
     
       9. The magnetron of  claim 8 , wherein a ratio of said second total magnetic flux to said first total magnetic flux is at least 1.5. 
     
     
       10. The magnetron of  claim 1 , further comprising a second auxiliary permanent magnet magnetized perpendicularly to said center axis and disposed between said inner and outer magnetic poles. 
     
     
       11. The magnetron of  claim 3 , wherein said nested unbalanced magnetron has a triangular shape. 
     
     
       12. The magnetron of  claim 3 , further comprising a second auxiliary permanent magnet magnetized perpendicularly to said center axis and disposed between said inner and outer magnetic poles. 
     
     
       13. The magnetron of  claim 5 , wherein said nested unbalanced magnetron has a triangular shape. 
     
     
       14. The magnetron of  claim 5 , further comprising a second auxiliary permanent magnet magnetized perpendicularly to said center axis and disposed between said inner and outer magnetic poles. 
     
     
       15. The magnetron of  claim 7 , wherein said nested unbalanced magnetron has a triangular shape. 
     
     
       16. The magnetron of  claim 1 , wherein said nested unbalanced magnetron has a triangular shape.